Jay Sean Throws Sing-Off Champs Nota Off-Key – Almost

For a split second, while singing their rendition of the Jay Sean hit Down, the a cappella sextet of Nota went speechless for the first time since appearing on The Sing-Off.

That’s because Jay Sean himself snuck up behind them and joined them onstage Monday after they won the musical competition.

When they called me up and said if Nota win, we would love for you to come out, surprise them and sing your song with them, I said, Oh my God, of course I will, Jay Sean tells PEOPLE. But one thing I knew, and I told them, was, Guys, you do realize there s actually no backing music. They are the music.’ So if they get surprised, which they will be, they ll stop singing! There will just be silence! Luckily, they re all such pros and they just kicked back in and we had fun.

A stunned and elated Nota, who traveled from Puerto Rico to compete, also received a congratulatory text message from Ricky Martin upon their win over Tufts University singers the Beelzebubs.

“We’re just grateful we were able to bring our music and that people enjoyed it,” says Nota member David Pinto, 25. “The competition was so tight,” adds Edgar Rios, 34. “All the groups were so amazing in their own style, and we’re really thankful for the fans and the people who voted for us. It’s amazing.”

Jose Rodriguez, 37, says, “We’ve been waiting for this for so many years. We are very passionate. This is the opportunity we’ve been dreaming of and are honored to be a part of this great show. We are so grateful.”

The short, four-episode series on NBC featured the talents of eight a cappella groups from around the country and offered the winner a $ 100,000 prize and a recording contract from Sony. Nicole Scherzinger from the Pussycat Dolls, Shawn Stockman from Boyz II Men, and singer-songwriter Ben Folds were judges.

“I’ve traveled and recorded university a cappella groups because I’m so interested in hearing people sing together,” says Folds. “This was an opportunity to help push them into the limelight. One of my missions in this was to let them show what an experience it is to be in the middle of people singing together and how a cappella music can separate itself from where pop music has gone, which is awesome, but as a more human experience.”

In the finale audience were stars Jack Black, Masi Oka and Peter Gallagher.